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Math and physics are extremely useful in determining lengths of circuits on brass instruments, but - when push comes to shove (as failed-to-be-observed additional mathematical and physical factors surely exist, which humans sometimes fail to observe) - the measuring of circuits that WORK - combined with trial-and-error - are the only ways to absolutely be assured of usable equipment.

The 12th root of 2 formula reports that a BB♭ tuba's #4 circuit should be roughly 70"in length, but I believe I'm observing that successful/usable (tuned) ones (at least, when they are wound around and such) are more like 73" - 74" long.

Rather than supposition (and/or bluster) has anyone taken the time to carefully physically measure a #4-valve four-step-lowering circuit on a BB♭ tuba - that ended up offering an in-tune length (ie. perhaps an in-tune "low F", combined with a typically slightly-flat C), and - if so - would they be willing to report their findings in this thread?

Obviously, I'm in the middle of cobbling one together (being initially pleased with the plumbing configuration I've been able to devise, which is in the rough neighborhood of that range of length), and would be fascinated to be able to read some accurately-measured successful results.

The length is whatever the engineers/science say it should be.

You just do what they say and if it sounds funny, well, that's on YOU!!

Unless you deny science...

Something which always makes me feel a bit uneasy is measuring around bends such as slide bows. Do you take your measurements from the inner or outer radius or the center line? Also what allowance is made for the distance within the valve itself? These could make for a fair difference, especially if several bends are involved.

It could be handy if old Karl Geyer's ball of string were available: it would be the distance between two particular knots. Sort of a case of, "how long is a piece of string?".

I don’t even know why tuning slides should be necessary.

The scientifically derived consensus on proper length is good enough for me!!

Disagree at your own peril.

Most I've measured (and built) hover around 73" (that's including the distance inside the valve port). Measuring valve knuckles accurately can be challengin, so oftentimes they are approximate at best.

Always better to make it a tad longer, then there's room to cut, if needed.

Art Hovey has a great treatise on circuit lengths, which are generally accurate within an inch or so.

http://galvanizedjazz.com/tuba.html

bravo!

Thanks!

How does everyone measure total bugle length?

Three Valves wrote: ↑Tue Dec 15, 2020 5:12 pm I don’t even know why tuning slides should be necessary.

The scientifically derived consensus on proper length is good enough for me!!

Disagree at your own peril.

A. E. Couturier approves.

There exist Couturier 4 valve baritones, one of which was recently featured in tuba tuesday. Would it be useful to measure that loop and multiply by 2?

(speaking of which, i haven't looked at the recent tuba tuesday yet... i have been remiss!)

humBell wrote: ↑Wed Dec 16, 2020 1:01 am
A. E. Couturier approves.

There exist Couturier 4 valve baritones, one of which was recently featured in tuba tuesday. Would it be useful to measure that loop and multiply by 2?

I saw that! It looks as though it were made in a French sausage factory.

LargeTuba wrote: ↑Tue Dec 15, 2020 7:52 pm How does everyone measure total bugle length?

Center line of all parts of the instrument, including valve crooks and tubing, using a cloth (or plastic) sewing tape.

To get a ballpark accurate bell length, I set the horn on its bell, and use a level across the point where it enters the bottom bow ferrule, and use a yardstick to measure the distance from the level to the floor/table.

I ventured into this area recently, wanting to compare the bell size of two big BBb tubas, at a position about a yard from the bell end. One of them however was bell front, with a significantly large bell flare. So I just kind of waved my tape in the general vicinity and called it good - luckily, it doesn't really matter at all.

My understanding is that the acoustical dimension of the bell, if you will, extends some distance past the plane of the bell flare, and that distance varies depending on the shape and size of the bell flare and possibly other considerations. And then there's the elbow. Maybe the acoustical dimension is square in the middle of the curve.

donn wrote: ↑Wed Dec 16, 2020 7:29 pm ...Maybe the acoustical dimension is square in the middle of the curve.

thanks...
' fairly sure that most believe this to be true...

My "science" is limited to:
> If it's good, I'll play it.
> If adding some wiz-bangs (that actually DO stuff) makes it good-er, I'll add 'em.